All Decked Out

Today on the home front: The paint expert at Williams Lumber dishes on staining pressure-treated wood

Lynn Hazlewood

We’re only halfway through April and it looks like mid-May — even the lilac is in bud. Spring is here! And with it comes the urge to throw open all the windows and fling your clutter out of them. At least, that’s my impulse — it would be so much easier than going through it, trying to sort trash from treasure.

Now is also the time we’re thinking about gussying up the back yard. A Do-It-Yourselfer posted this question: “Any advice for staining a relatively new deck? I’ve heard to wait a year for the chemicals to seep out of the pressure-treated wood. I have spots of mold that have formed in the past year.”

As a green advocate, I shudder at the idea of chemicals seeping out of pressure-treated wood — wasn’t there a brouhaha a while back about arsenic? I called Williams Lumber’s flagship branch in Rhinebeck for info. “No, no, that was an overblown concern,” says Roger Renwick. (He’s head of the paint and stain department, but the guys at Williams know about all kinds of things.) “The new pressure-treated wood is safe. It used to have trace amounts of arsenic that would leach out, but they discovered a child would need to eat about 80 pounds of it to be poisoned, and I don’t know any kids that like wood that much.” Hmmm. The mind reels wondering how they determined the safe amount for a child to ingest. Online I found a report of three horses who died after chewing it, so my advice is don’t, even if it is safer these days.

Anyway, to answer your question, DIY-er: Renwick says you only have to wait long enough for your deck’s wood to be completely dry before you stain it. If it’s been around long enough to grow mold, you’re safe, but you’ll have to get the mold off. Renwick recommends using a power washer and a cleaning fluid formulated for decks. There’s a green version, but it’s not as effective against mildew. Don’t try to spot clean the mold because you’ll make the wood patchy.

After you’ve power-washed, he says, “You need a good week of drying weather, with drying winds. Five days should do it.” Once the wood is thoroughly dry, you can start sloshing on the stain. Pressure-treated lumber often has a green cast (it’s sometimes called green-treated — environmentalists take note), so you may want to choose a tinted one to smarten things up. Renwick recommends an oil-based, semi-solid Cabot stain, and so do I. We used Cabot on our barn and it still looks terrific six years later. We went for the water-based version, but the barn siding doesn’t get any foot traffic unless you count squirrels. Cabot comes in any color you want, and Williams has the computer matching gizmo if you want to tweak it to something. If you get into the swing of it, you can stain your wood furniture in to match, or in contrasting shades.

How long will the staining job hold up? Renwick says it depends. “Exposure, how high the deck is, what vegetation is nearby, the space between the boards — a whole bunch of criteria. Could be a year, a year-and-a-half, anything up to five years.”

For those thinking of adding a deck: cedar and redwood are more expensive, but easier woods to install than pressure-treated, and they have natural rot and insect resistance. And, says Renwick, “they’re real easy to treat with a clear preservative. If you do it every year, you’ll have a cedar deck forever, unless termites get at it.”